The present invention relates to the art of testing specimens for resistance to deterioration due to sunlight and humidity. It finds particular application in conjunction with a materials test chamber having a controlled multiple-blower system to achieve simultaneous air and black panel temperature control and/or relative humidity control. However, it will be appreciated that the invention has broader applications and may be advantageously employed in connection with other accelerated weather testing devices and concepts.
In accelerated weather testing, a specimen is supported within a test chamber and exposed to ultraviolet fluorescent lamps, such as xenon lamps. Typically, outside air or fresh air is heated and blown into the interior of the test chamber in order to regulate the temperature within the chamber. In addition, humidity is added to the chamber in the form of evaporated water. In the above-described weathering apparatus, one example of the machine's operation includes applying ultraviolet light rays to one or more specimens of a set temperature for a given period of time. The lamps are then turned off and the interior of the chamber is kept at the same or a different temperature for a set period of time. Further, humidity may be added to the system in a repeated fashion. Accordingly, specimens are wetted, exposed to ultraviolet rays, and dried in a repeated fashion.
In the weathering system described above, the chamber air temperature (CAT) is regulated using a single blower system, that is a single blower which draws outside or fresh air into the system, along with a damper to regulate air flow. While the single blower system is fairly adequate for controlling chamber air temperature, it is inadequate for precise humidity control as well as simultaneous control of the CAT and black panel temperature (BPT). Typically, black panel temperature is measured using a temperature sensor placed on the specimen support to measure the actual black panel temperature, that is, the temperature of a dark specimen disposed within the test chamber. Because a single blower and damper system is not fully equipped to effectively regulate both chamber air temperature and black panel temperature along with precise humidity control, a need exists for a system and control method for simultaneous control of both CAT and BPT.
The present invention is directed to a multiple blower system and control method for the simultaneous regulation of chamber air temperature and black panel temperature, which overcomes the above-referenced problems and others.